The present invention generally relates to dissipation of heat generated by electronic devices, and more particularly to a heat sink assembly and method of affixing the heat sink assembly to electronic devices.
The cooling of integrated circuit devices is necessary to ensure their proper operation and to extend their useful life.
A trend in contemporay integrated circuit design is to position multiple integrated circuits on a printed circuit board in an array. A consequence of providing an array of integrated circuit devices on a printed circuit board which operate at relatively high speeds is substantial heat production which may be detrimental to these electronic devices. Thus, a need exists for efficient and convenient methods and apparatus for thermal management of integrated circuit arrays and similar type devices.
Various designs of apparatus that cool integrated circuit devices have been developed. For example, U.S. Pat. No. 5,397,919 discloses a heat sink assembly adapted for use with an electronic device package such as a microprocessor. The apparatus includes a threaded base of a finned heat sink adapted to be received in a threaded bore of an adapter which mounts onto the electronic device package. Desired thermal coupling is achieved by screwing down the heat sink in biasing engagement with the package.
Another example is U.S. Pat. No. 5,168,348 which teaches an impingement cooled compliant heat sink comprised of a metal sheet that is brought into contact with chips on a multi-chip module. The metal sheet acts as a spreader plate for jet impingement immersion cooling with a fluorocarbon, liquid nitrogen, or other dielectric liquids. Slots and/or holes in the sheet located between the chip sites serve to: (1) create flexible joints in the sheet between the chips to permit conformity to neighboring chip sites, (2) allow for clearance of decoupling capacitors and other structures on the substrate between the chips, and (3) permit the dielectric coolant to flow through the plate so that there will be no pressure difference across the compliant heat sink.
Yet another example is U.S. Pat. No. 4,654,754 which describes a thermal link between a heat source and heat sink that compensates for irregularities on the surface of the aforementioned components and/or nonuniformity in the spacing therebetween. The thermal link utilizes a spring metal device having a free arm which allows the link to align itself under low pressure so that it is in intimate contact with both the heat source and heat sink. Another embodiment utilizes an elastomeric material filled with thermally conductive particles to form a mat that has a plurality of raised sections having air spaces between each of the sections. The raised sections deform under low pressure by expanding laterally into the air spaces to conform to the space between the heat source and the heat sink.
U.S. Pat. No. 4,838,347 describes a compressible thermally conductive member comprising a polymer field with thermally conducting, magnetically aligned particles comprising a base portion and a multiplicity of protrusions extending from at least one surface of the base portion. At least when compressed, a thermal path exists across the thickness of the thermally conductive member.
U.S. Pat. No. 5,270,902 teaches a heat transfer device for use with a heat sink in removing thermal energy from an integrated circuit chip. The device includes a first membrane of flexible, thermally conductive material having a first surface in contact with the integrated circuit chip. A flexible, thermally conductive radial finger spring is disposed in contact with a second surface of the first membrane. A second membrane of flexible, thermally conductive material is included. The second membrane has a first surface in contact with the spring and a second surface in contact with the heat sink.
U.S. Pat. No. 5,285,108 teaches a cooling member for an integrated circuit, the member has a recess therein for receiving the integrated circuit and contacting a portion of the exterior surfaces of the integrated circuit and a portion of metal leads extending from the integrated circuit; in one aspect, such a member has a plurality of such recesses for accommodating a plurality of such integrated circuits; and in one aspect, such a system includes a metal heat sink.
U.S. Pat. No. 5,265,321 discloses an integrated circuit structure and method of making in which the circuit has a plurality of metal exchanger elements spaced from each other with their first ends secured to the structure. The first ends may be adhesively secured to an integrated circuit chip or the underlying substrate, and the heat exchanger may be hermetically attached. The method uses a compliant removable support block for attaching the plurality of individual heat exchanger elements to integrated circuit structures having variations in their elevation.
U.S. No. 5,353,193 teaches a removable heat sink assembly comprised of a heat sink unit and heat spreader. The heat sink unit has at least one fin and a coupling collar for radiating heat away from a packaged electronic device. The heat spreader includes a platform attached to an inner collar in thermal contact with the packaged electronic device. The platform has one or more tabs suitable for mating with one or more flanges located on the coupling collar of the heat sink unit. Coupling grooves within the flanges engage the platform of the heat spreader when the flanges are mated with the heat spreader tabs and the heat sink is turned. The heat sink can therefore be quickly and conveniently attached to or removed from the heat spreader.
Some prior art approaches to thermal management of packaged electronic devices require the mating of individual heat sinks with individual components. The problem with this approach is that the use of individual heat sinks is expensive and the associated installation is very labor intensive. Also, function and appearance can be a problem with this approach unless each heat sink is accurately aligned with its neighbor. However, the aforementioned alignment is also labor intensive.
The use of some prior art heat sinks adapted for cooling a multiplicity of integrated circuits can also present problems. For example, some heat sinks require that each contacting surface of the of the individual integrated circuit devices be co-planar to establish an effective thermal link. Moreover, other types of heat sinks do not allow the replacement of one of the multiplicity of heat sinks without removing the entire heat sink from contact with all or most of the heat sinks. The aforementioned draw backs increase the labor and cost of maintaining arrays of integrated circuit devices requiring thermal management.